DC--DC converters are normally used as constant DC voltage power supplies. The desirability of having a DC--DC converter that provides a number of different voltage outputs to a number of different independent loads has been recognized. There is a continuing need for such a circuit which has the advantages of clamped mode circuits, is of relatively simple construction and relatively inexpensive, and which provide stable voltage levels to a number of independent loads that, if desired, can be electrically isolated. With electrical isolation, noise, impedance changes, and the like from one load would not affect the power transmitted to another load.
Multiple output DC--DC converters providing a regulated voltage have typically required separate outputs provided by separate transformer windings as well as independent direct voltage regulating controls for each output where precise regulation is required. In a typical forward or flyback converter with multiple outputs, the non-conduction intervals of the power switch may result in a non-continuous transfer of energy to the output which results in an inefficient transfer of energy to the output.
Power converters have utilized synchronized rectifiers because of their compact size and high efficiency. Self synchronized rectifiers refer to rectifies using MOSFET rectifying devices having control terminals which are driven by voltages of the windings of the power transformer in order to provide the rectification of the output of the transformer. However, post regulated multiple output topologies suffer in efficiency, particularly when synchronous rectifiers are self-driven.
A need has thus arisen for an improved converter utilizing self-driven synchronous rectifiers.